Indo Datnoids question

Hi there, I just purchased 5 Indo Datnoids from my local fish store. They look really nice in the store however when I took them home they changed from gold to black.... Can anyone explain to me why they do that. Its been a few days now and they are still black with black bars.... I did a little research about them and found out that Datnoids has stable and unstable times. How would I be able to make them stable again where they show nice colors like when I saw them in the store? Thanks for your help..

 

Probably stress, check your parameters and make sure they match the fishes needs. Make sure you enough cover for them to be happy.

 

I dont think they are stress.... its been a few days now and they eat well. They are in my 240gal tank with my Jardini.